Conventionally, when drawing is performed for a workpiece by means of a press, a die cushion device is employed. The conventionally employed die cushion has been disclosed in Japanese Examined Utility Model Publication No. 2-25538. The disclosed die cushion comprises an air cylinder for elastically supporting a pad for providing a cushion and a hydraulic cylinder for controlling lowering speed of the pad. A flow rate of a working fluid discharged from the hydraulic cylinder is controlled by a numerically controlled servo valve so that necessary cushion force corresponding to the drawing process can be obtained.
However, the die cushion device comprising the air cylinder and the hydraulic cylinder, is large in size so as to require a large space for installation. Furthermore, since an expensive servo valve must be incorporated, the device per se becomes complicated and expensive.
In addition, in case press molding is to be performed through a plurality of steps, since each individual die cushion device is large in size and expensive as set out above, it is often practically impossible to install such die cushion devices for respective process steps in view of installation space and cost.